A portable device (smartphone, personal digital assistant (PDA), tablet computer or the like) includes a liquid crystal display device. The liquid crystal display device includes an array substrate (may be referred to as a first substrate) and counter substrate (may be referred to as a second substrate), and a liquid crystal layer is formed between the first substrate and second substrate. This configuration is referred to as a liquid crystal display panel in some cases.
The first substrate includes a plurality of pixel circuits arranged in a matrix form. A pixel circuit is formed in the vicinity of an intersection of a gate line (or may be referred to as a scanning line) and source line (or may be referred to as a signal line). When a pixel circuit is selected by a gate signal supplied to the gate line, a pixel signal supplied from the source line is written to the pixel circuit.
The gate signal is output from a gate circuit formed on the first substrate to the gate line, and a source signal is output from a source selection circuit formed on the first substrate to the source line. Incidentally, as an element configured to control the operation timing of each of the gate circuit and source selection circuit, and supply a source signal to the source selection circuit, a liquid crystal display driver is utilized. This liquid crystal display driver is constituted as one semiconductor chip.
The above-mentioned liquid crystal display driver, i.e., the semiconductor chip includes an oscillator, timing controller, and the like in addition to a panel control signal generation circuit. Further, the semiconductor chip can drive a liquid crystal display panel according to a sequence of the timing controller.
Recently, image resolution enhancement of the liquid crystal display panel of a portable device is desired. For example, a liquid crystal display panel capable of displaying an image called 4K2K having 3840 pixels in the horizontal direction, and 2160 pixels in the vertical direction is desired. Further, there is a strong possibility of a device capable of displaying a super-high-resolution image called 8K4K having 7680 pixels in the horizontal direction, and 4320 pixels in the vertical direction being desired.
Further, in order to drive a liquid crystal display panel configured to display a super-high-resolution image, it becomes necessary to make various improvements in the function of the liquid crystal display driver. That is, being capable of driving the liquid display panel at high speed, and being capable of supplying source signals (R, G, B signals) in which the number of bits, and number of pixels are enormously increased because of the high resolution of the liquid crystal display panel to the liquid crystal display panel.
However, there is a limit to realizing a liquid crystal display driver that satisfies the above requirements by using one semiconductor chip in terms of the integration technique. Thus, a method for driving a liquid crystal display panel by using a plurality of liquid crystal display drivers (semiconductor chips), and operating the liquid crystal display drivers in parallel with each other is now investigated.